In order to send a satellite into its operational orbit and thereafter ensure that it holds its station for the operational life of the satellite, propulsion means need to be provided. As a general rule, a device comprising at least one tank containing a propellant that is pressurized is used.
What is meant by a “propellant” is a substance used on its own or in combination with other substances and intended to provide energy.
A distinction is made between various types of propellant propulsion devices:                A bipropellant device comprising two tanks containing the propellants. It further comprises a pressurizing gas tank containing, for example, helium at high pressure, the pressurizing gas pressurizing the propellants.        A monopropellant device comprising a tank divided into two compartments by a membrane: one compartment containing the propellant, generally hydrazine, and one compartment containing a gas that presses against the membrane so as to pressurize the propellant.        There are also membraneless monopropellant devices, the structure of which is similar to that of the bipropellant devices.        
FIG. 1 is a functional diagram of a bipropellant propulsion device according to the known art.
The bipropellant propulsion device 1 comprises a low-pressure first part 2 and a high-pressure second part 3.
The low-pressure first part 2 notably comprises two propellant tanks 4. In this particular instance, the propellants 5 used contain MMH which is the acronym for monomethylhydrazine and MON the acronym for mixed oxides nitrogen.
The high-pressure second part 3 comprises at least one tank, in this particular instance it comprises two tanks 6 containing a pressurizing gas 7, in this instance helium, the pressurizing gas 7 being at high pressure, around 300 bar, before the satellite enters orbit.
The pressurized helium 7 is injected via pipes 8 and a pressure regulator 9 into the propellant tanks 4 to pressurize the propellants 5, the regulated pressure in the pipes 8 downstream of the pressure regulator 9 being of the order of 20 bar.
In other words, all the pipes 8 situated in the second part 3 upstream of the pressure regulator 9 contain pressurizing gas 7 at high pressure, and the pipes 8 situated in a part 2 downstream of the pressure regulator 9 contain pressurizing gas 7 at low pressure.
In the second part 3, the pressure prior to the launching of the satellite is comprised between 200 and 300 bar. After the operational orbit has been entered, the pressure in the second part 3 is comprised between 30 and 50 bar. Downstream of the pressure regulator 9, the pressure is around 20 bar.
A PV1-NC valve 10 of the nominally “closed” type is positioned between the pressurizing gas tank 6 and the pressure regulator 9. This PV1-NC valve 10 allows pressurizing gas 7 to be conveyed to the pressure regulator 9 when the nozzles 11a, 11b are in operation, notably at the moment that the satellite enters its orbit and its holding station.
The principle of operation of the device according to the known art can be summarized as follows.
While the tanks 4 are being filled with propulsion reagents and the tanks 6 are being filled with pressurizing gas, the PV1-NC valve 10 is in the “closed” position.
Upon the launching of the satellite, the PV1-NC valve 10 is opened, the pressurizing gas 7 is introduced under a pressure of around 20 bar into the propellant tanks 4. The pressurized propellants 5 are then injected into the nozzles 11a, 11b. 
The quantities of pressurizing gas 7 and of propulsion reagents 5 needs to be sufficient to serve the launching of the satellite into its operational orbit, to ensure that the satellite holds station in its operational orbit, and to bring the satellite onto its final orbit when the satellite reaches the end of its service life.
These days, satellites at the end of their service life contain residual sources of energy, such as pressurizing gases or propellants.
According to a new LOS (the acronym for “low orbital spatial”) regulation that is coming into force in 2020, all energy sources present within a satellite need to be eliminated when the satellite reaches the end of its service life.
A first solution envisaged in order to meet the LOS regulations is to isolate the second part 3, notably, using a PV7-NO valve 12 of the type that is “open” in nominal mode, positioned in such a way as to isolate the first part 2 from the second part 3 when the satellite is in its operational orbit, and to add an operable pyrotechnic valve of the “closed” type at the second part 3.
When the decision to put an end to the operation of the satellite is taken, the pyrotechnic valve of the “closed” type positioned in the second part 3 is actuated in order to discharge all of the remaining pressurizing gas, it being possible for any residual propellants 5 to be discharged via the nozzles 11a; 11b. 
However, this solution presents certain disadvantages, notably:                the addition of an extra approximately 300 g of mass notably corresponding to the pyrotechnic valves and the supports thereof. Now, any excess mass onboard a satellite represents a not-insignificant on-cost.        the need to test in order to ensure correct operation of the pyrotechnic valve, requiring additional labour.        